The invention relates to a flat miniature dynamoelectric machine.
Motors or generators incorporating a flat rotor which is supported by a commutator in order to minimize the axial thickness and the overall size of the machine are already known, and are commonly referred to as flat miniature dynamoelectric machines. An electric motor of this type may be used in a small size electrical instrument such as pocket type tape recorder, and in such applications, it is essential that the various parts of the structure be precisely machined to avoid a degradation in the precision which is likely to occur in an instrument of small size. In particular, a high degree of precision is required for the mounting of the motor shaft since any positional error of the shaft may upset the positional relationship between the rotor and the magnet or between the commutator and the brushes, causing a degradation in the performance of the machine.
In conventional dynamoelectric machines of this type, a single washer or a plurality of washers are utilized to provide a thrust bearing. In this instance, friction occurs between one of the washers and an adjacent member or between the washers themselves, and it is necessary to be able to supply a variety of different thicknesses in order to permit a desired positioning with a sufficient degree of accuracy. Alternatively, an anti-abrasion disc, may be disposed at the bottom of an opening which receives one end of the shaft, in order to serve as a thrust bearing. However, the position of abutment between the shaft end and the disc is subject to variation, which required a troublesome centering operation for the shaft. In addition, the opening must be machined to a high accuracy.